Molybdenum Cofactor Synthesis 3 (MOCS3)

MOCS3 is thought to catalyze both the adenylation and subsequent generation of a thiocarboxylate group at the C terminus of the smaller subunit of molybdopterin synthase, MOCS2A.The deduced 460-amino acid protein has a calculated molecular mass of 49.7 kD. It contains an N-terminal MoeB domain and a C-terminal rhodanese (TST)-like domain (RLD). Fluorescence-tagged MOCS3 showed a cytoplasmic distribution in transfected HeLa cells.

In a defined in vitro system for the generation of molybdopterin from a precursor, the sulfurated form of MOCS3-RLD was able to provide the sulfur for the thiocarboxylation of MOCS2A. Mutation of the putative persulfide-forming active site cysteine (cys412) abolished the sulfurtransferase activity.